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Question

What force is required to accelerate a lawnmower of mass 12 kg to 4.5 km/h from rest in 3.0 s (neglecting friction)? [5.0 N]

Update:

a) if there is friction present and mu k =0.80 , what force is required now? [99 N]

Answer 1

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4.5 km/h x 1000 m/km x 1 hr/3600s = 1.25 m/s

acceleration = ΔV/Δt = 1.25/3 = 0.417 m/s²

F= ma = 12•0.417 = 5 N

weight = mg = 12•9.8 = 117.6 N

friction force = 117.6 x 0.8 = 94 N

required force = 94 + 5 = 99 N